/Engine/Source/Runtime/Engine/Classes/Components/PrimitiveComponent.h
Does the actual work for welding.
true if did a true weld of shapes, meaning body initialization is not needed
virtual bool WeldToImplementation ( [USceneComponent](API\Runtime\Engine\Components\USceneComponent) * InParent, [FName](API\Runtime\Core\UObject\FName) ParentSocketName, bool bWeldSimulatedChild )